1. Field of Invention
This application relates to magnetic switching devices and systems, and more particularly to magnetic switching devices and systems for controlling embedded electrical devices.
2. Discussion of Related Art
Currently in the United States, there are thousands of patients implanted with electrical devices, for example, but not limited to, pacemakers and/or implantable cardioverter-defibrillators (ICDs). A pacemaker, also called an artificial pacemaker, is a device which uses electrical impulses, delivered by electrodes contacting the heart muscles, to regulate the beating of the heart. An ICD is a small battery-powered electrical impulse generator which is implanted in patients who are at risk of sudden cardiac death due to ventricular fibrillation and ventricular tachycardia. The ICD is programmed to detect cardiac arrhythmias and correct it by delivering a jolt of electricity.
Many patients with such electrical devices will require non-cardiac surgery or procedures at some point during their lifetime which may interfere with their electrical devices. Non-cardiac surgery may include the use of electrocautery during surgery, lithotripsy, for treatment of kidney stones, the use of a transcutaneous electrical nerve stimulation (TENS) device, or radiation therapy in the treatment of cancer. This presents a serious problem, as many electrical devices are sensitive to electromagnetic interference (EMI) from other electrical devices used during surgery. Consequently, many implantable devices are designed with a magnetically operable switch to shut off the device or switch it to a “backup mode” when a magnetic field is applied. For example, a patient's pacemaker exposed to EMI may malfunction. Similarly, a patient's ICD may mischaracterize EMI as ventricular fibrillation (VF) and may deliver a shock to the patient. VF is a condition in which there is an uncoordinated contraction of the cardiac muscle of the ventricles in the heart, making them quiver rather than contract properly.
Several methods have been adopted to avoid the influence of EMI on an imbedded electrical device during surgery. However, these methods have some serious limitations. For example, one solution in avoiding EMI is to reprogram the magnetically-switchable device. However, reprogramming generally requires a technically skilled person to be present to reprogram each device, making reprogramming an expensive option.
Another known solution is to place a magnet over a magnetically-switchable, electrical device to inactivate or place the device in a backup mode. The type of magnet used is usually a large permanent magnet, such as a donut magnet. Needless to say, it is difficult to position and to ensure that the magnet stay in place during surgery. Shifting of the magnet during an operation could reactivate the magnetically-switchable, electrical device, for example the pacemaker or ICD, and put the patient at risk.